Transplantation of organs has become a widely practiced medical procedure. Organs such as a heart, lungs, kidney, pancreas and liver may be harvested from a donor and transplanted in a recipient. Although the risk of organ rejection has been reduced by the discovery of immunosuppressant drugs such as cyclosporine, organ rejection remains a major complication for patients undergoing organ transplantation.
A body receiving a donated organ naturally treats the organ as foreign tissue. The immune system of the recipient, which protects the body from infection, attacks the transplanted organ and tries to destroy it. Immunosuppressant drugs suppress the immune system so that the new organ will not be attacked and damaged. Organ recipients take immunosuppressive drugs for the rest of their lives to ward off rejection.
Even with immunosuppressive therapy, however, the immune system may try to reject the organ. Consequently, transplant recipients should be monitored for signs of rejection. Rejection typically manifests itself as inflammation in the organ, accompanied by edema. Conventional monitoring of organ rejection may be invasive or non-invasive. Conventional non-invasive techniques generally monitor rejection indirectly, such as by monitoring changes in blood chemistry. A conventional invasive technique is a tissue biopsy, in which a physician inserts a biopsy needle through the skin into the organ, and takes a sample of the transplanted organ for inspection under a microscope. Following transplant surgeries, biopsies may be performed frequently, but biopsies are usually performed less frequently following recovery.